A Microwave Reflection Readout Scheme for Hot Electron Bolometric Direct Detector

In this paper, we propose and present data from a fast THz detector based on the repurpose of hot electron bolometer mixers (HEB) fabricated from superconducting NbN thin film. This detector is essentially a traditional NbN bolometer element that operates under the influence of a microwave pump. The injected microwave power serves the dual purpose of enhancing the detector sensitivity and reading out the impedance changes of the device in response to incident THz radiation. We have measured an optical Noise Equivalent Power of 4 pW/ ${\surd{\hbox{Hz}}}$ for our detector at a bath temperature of 4.2 K. The measurement frequency was 0.83 THz and the modulation frequency was 1.48 kHz. The readout scheme is versatile and facilitates both high-speed operation as well as multi-pixel applications.